1. Field of the Invention
The present invention relates to a time stamp correction apparatus and a time stamp correction system.
2. Related Background Art
In some cases, devices connected to a network share time information (network time). If there are a plurality of networks, unique network time is administered to every network.
A device transmitting real time data (transmitting device) generates information of time (time stamp) for the real time data to be reproduced in a receiving device, on the basis of network time in a network to which the transmitting device belongs itself. This time stamp is calculated by adding an offset value to the network time. The transmitting device transmits the generated time stamp to the receiving device together with the real time data as a real time packet.
After receiving the real time packet, the receiving device processes real time data synchronized with the network time, on the basis of the time stamp contained in the real time packet. The receiving device temporarily retains the received real time packet in an internal storage device (FIFO (First In First Out)) until data processing is started.
The network (first network) to which the above-described transmitting device and receiving device belong is connected to (integrated with) a different network (second network) in some cases. Network time in the network after integration is unified into the network time of either the first network or the second network. If the network time after integration is made equal to the network time of the second network, discontinuity occurs in the network time of the first network including the above-described transmitting device and receiving device.
If in this case a real time packet is already retained in the FIFO in the receiving device at the time of the network integration, a time stamp in this real time packet is based on the old network time before the integration. This results in a problem that the receiving device cannot continue data processing while maintaining real time quality.